Devices for orthodontic and orthopedic expansion or contraction of the maxilla are known. Such known devices may comprise means for anchoring the device to two or more molars positioned on opposite maxillary half-arches divided by the median antero-posterior axis. The devices further comprise thrust or traction agents affixed to the anchoring means and acting in a direction substantially perpendicular to the antero-posterior axis, i.e., in the direction of distancing the two anchoring molars from each other or of moving them closer together.
At present there are two known types of these devices. In a first known type, the thrust or traction agents are of the wrench or screw type. More particularly, a structure composed of conjunction and of stiffening elements connects the anchoring means of each of the two opposed molars to two terminals which each present at least one threaded opening coaxial respective to each other, with the threads running in opposite directions. A pin having two threaded ends, with the threads running in opposite directions, is engaged in the corresponding threaded openings of the two terminals. A middle portion of pin includes means for actuating the pin in rotation, such as with the use of suitable instruments. By rotating the threaded pin, it is therefore possible to move the two terminals farther away or closer together, to thereby control the expansion or contraction action of the maxilla.
Despite that the above-described types of devices make it possible to exert forces of expansion or contraction perfectly oriented in a direction perpendicular to the antero-posterior median of the maxilla (i.e., parallel to the direction of expansion or contraction desired), an appreciable disadvantage of these devices is that the expansion or contraction action is of very short duration once the "loading" action (i.e., the twisting of the pin) is terminated. The short duration is the result of the loading structure being essentially rigid. Moreover, these devices do not allow an expansion or contraction action of a desired amount to be exerted in a progressive manner. Rather, the traction or expansion force is exerted on the teeth in an almost "traumatic" manner (i.e., all at once or over an extremely limited length of time).
The application of these devices therefore is especially painful for the patient. Furthermore, this mode of operation of the device means that the medical personnel must execute frequent adjustments and trials with the thrust or traction means in order progressively to achieve, in small increments, the desired effect of expansion or contraction of the maxilla.
A second known type of device makes it possible to overcome the drawbacks of this first known type that relate to the rigid structure of the thrust and traction means. More specifically, in the second type of known device the thrust and traction means are made up of elastic elements that, in the application phase, are pre-loaded to a pre-set level. Presently, the elastic means are made up, however, of a metal wire that presents a certain elasticity and that is bent in such manner that it exerts an expansion or contraction force. To exert the force in the expansion direction, for example, the elastic metal wire may be bent in such manner as to form a handle with its terminal portions spread apart. While to exert a force of traction, the metal wire may be bent in such manner as to form, for example, a spiral with end parts that intersect each other.
These elastic means exert a progressive action of expansion and compression that, however, because of their structure, is of very short duration, requiring frequent interventions for additional loading of force by means of further deformations. This type of device presents an additional drawback of causing the support teeth to unacceptably tip from the desired vertical orientation and to cause an undesirable V-shaped gap in the arch form (anterior vestibulation).
It is therefore an object of the present invention to create an orthodontic and orthopedic device in such a manner that it does not suffer from the above-described drawbacks of the presently known devices. It is also an object of present invention to provide a low cost device that is simple to install and adjust.